1. Field of the Invention
The present invention relates to cellular telecommunication systems, more particularly to a method and apparatus for detecting malfunctions of base station transceivers in a cellular telecommunications network.
2. Description of the Prior Art
A cellular telecommunications network typically comprises a variety of dedicated nodes, each one performing a specific task. These nodes comprise, among other types of nodes, at least one Mobile Switching Center (MSC) communicating with at least one Home Location Register (HLR), and a plurality of Base Stations (BS). The MSC is the switching entity of the cellular telecommunications network that is responsible for establishing and controlling the communications between subscribers. The HLR is another dedicated node which typically comprises a subscribers profile database that includes subscriber related data, such as the current location of the subscriber, the allowed services for each subscriber, and possibly the billing data. Each BS is responsible for the radio communications between the subscribers"" Mobile Stations (MS) and the cellular telecommunications network. Such a BS typically comprises at least one antenna, one base station controller, and a base station transceiver unit. The base station controller controls call set-up and the operation of the base station transceiver unit. The base station transceiver unit typically comprises a plurality of base station transceivers and each such transceiver handles actual radio transmissions, to and from a number of MSs, on selected radio frequencies. Typically, each BS transceiver has a number of assigned frequencies, or channels, that are used for establishing downlink and uplink transmissions with the MSs for communication or for signalling purposes.
In order to provide the best quality of radio service to cellular subscribers, the cellular operators have to regularly monitor the state of each BS transceiver. Radio transmission faults regularly occur and in many cases poor speech quality, poor system access, and poor reliability is due to transceiver malfunctions. However, it is the duty of the cellular operator to try to provide the best possible quality of service. Therefore, the industry has provided various methods for monitoring the state of the BSs, particularly the state of the BS transceivers which are directly responsible for the radio communication between the network and the cellular subscribers.
One of the most common methods involves periodic transmission of transceivers status information or alarms from the BS to the MSC which forwards this data to an Operation Support System (OSS) where the transceivers status information is stored in a database. Then, periodically, this data is manually checked and verified by network administrators. When an error is detected or suspected in a BS, technicians are typically sent on site in order to fix the problem.
However, this method is not well adapted to the needs of today""s cellular telecommunications networks. The status of a BS transceiver can be ok, or the transceiver performance can be above an arbitrary threshold defined by the network administrators, but the transceiver can still provide poor performance, such as poor voice or data transmission quality. The means currently used for detecting the possible faults or malfunctions within the BS are not reliable since they only use arbitrary parameters and pre-defined thresholds to distinguish between the well functioning and the malfunctioning transceivers. Additionally, the human intervention in analysing the transceiver information leads to inconsistent and heterogeneous analysis.
By using arbitrary and human-defined thresholds for detecting when a transceiver becomes faulty, the current systems are not sufficiently reliable. Moreover, often times they do not take any action for correcting poor service provided by particular faulty transceivers. Alternatively, when a particular error affects a plurality of transceivers within the same BS or the same service area, the current systems detect that each one of these transceivers provides a service quality lower than the pre-defined threshold, and based on this information, the operators may turn off all the transceivers, which results in the total loss of cellular service.
It would be useful to have a method for automatically and adaptively detecting a transceiver malfunction based on transceiver information wherein the threshold for detecting a malfunctioning transceiver would depend on the current average quality of service of transceivers serving a selected service area, or a portion thereof, such as for example a cell. It would be also useful to have a method for automatically and consistently detecting a transceiver malfunction by sorting the transceiver state information received from one or more BSs, on a per transceiver basis in order to detect a malfunctioning transceiver based on a preselected function of transceiver-related parameters, and when such a potentially malfunctioning transceiver is detected, to confirm the malfunction, and suggest or take an action, such as turning off the particular malfunctioning transceiver.
It is therefore an object of the present invention to provide an adaptive method and corresponding apparatus for adaptively detecting a BS transceiver malfunction by comparing the performance of a particular monitored transceiver with threshold performance proportional to the average performance of a plurality of transceivers from the same service area, cell or portion thereof.
It is a further object of the present invention to provide a method and corresponding apparatus for detecting the source of the malfunction of a BS transceiver, once a possible malfunction is detected for that particular transceiver. Preferably, the method for detecting a BS transceiver malfunction and the method for confirming the malfunction are used in conjunction with each other for both detecting and confirming a base station transceiver malfunction.
According to a first preferred embodiment of the invention, there is provided a method for detecting malfunctions of base station transceivers, the method comprising the steps of:
a) sorting information relating to a plurality of base station transceivers on a per transceiver basis and generating a service quality value for each one of said plurality of base station transceivers, said service quality value being representative of a performance level of each one of said plurality of transceivers;
b) computing a service quality threshold value through a function generating a result proportional to an average performance level of said plurality of transceivers, using said information relating to said plurality of transceivers; and
c) for at least one particular transceiver from said plurality of transceivers, comparing said service quality value with said service quality threshold value for determining the acceptability of said performance level of said particular transceiver.
According to a further embodiment of the invention, there is provided a method for confirming the source of a malfunction detected in a base station transceiver, the method comprising the steps of:
detecting a first transceiver suspected to be malfunctioning, said first transceiver having assigned a first set of frequency channels;
selecting a second transceiver having assigned a second set of frequency channels, said second transceiver appearing to be properly functioning;
assigning the second set of frequency channels to the first transceiver; and
detecting if the first transceiver persists malfunctioning, whereby when the first transceiver persists malfunctioning the most probable cause of the malfunction is one of a hardware problem and a software problem, and when the first transceiver stops malfunctioning the most probable cause of the malfunction is a frequency interference.
According to yet another further embodiment of the invention, there is provided a transceiver malfunction detector for detecting malfunctions occurring in transceivers of at least one base station of said system, said transceiver malfunction detector comprising:
at least one database for storing information relating to a service performance of a plurality of base station transceivers;
means for generating a service quality value for each one of said plurality of transceivers by sorting said information on a per transceiver basis, each said service quality value being representative of a performance level of one transceiver;
means for generating a service quality threshold value proportional to an average of the service quality values of said plurality of transceivers; and
means for comparing said service quality value of at least one transceiver from said plurality of transceivers with said service quality threshold value for determining the acceptability of said performance level of said at least one transceiver.